Random LED flasher

Can anyone help me build a random 2-LED flasher?? I've seen projects for flashing LED's but they all have fixed intervals... what I'm looking for is a circuit that would flash 2 LED's at the same time then flashes again with indefinite intervals... around 1 - 2 seconds intervals would be fine but again, random... your help will be greatly appreciated...

So both led's ALWAYS flash at the same time?

Maybe not as complicated as you are looking for... but, I once bought a bunch of flashing red LEDs cheap ($5/100). They seem to flash ar different frequencies. I've been using 5 wired in parallel to discharge a small rechargable lithium battery I have been playing with for a couple of weeks (using LEDs as solar cells). Get pretty interesting, and apparently random patterns.

There are are dozens of 2 transistor circuits to flash LEDs on the web, will take a look later, might have on on my HD to post. But if you put together 2 identical circuits, they will flash at slightly different frequencies due to component tolerances (caps and resistors).

Have seen, and likely have a copy, of a circuit using a 4xxx CMOS chip, that flashes randomly. Just seemed like a lot of pins for something I could do with an 8-pin AVR chip.

TrevorP said:

So both led's ALWAYS flash at the same time?

Click to expand...

that's right... i want to flash a red and orange LED at the same time... no programming please.. i dunno anything about that stuff...

I do not know of any LEDs that blink randomly. My LEDs have a blink rate or a blink pattern.

Is this an experiment? Do you have an application where thousands will be used?

What you want is a pseudo random number generator. Adapt something like this to drive the LEDs:
**broken link removed**

You can build a simple psuedo random generator with some flip flops or shift register ICs. For example, my old Forrest Mims "Engineers Notebook" has a simple pseudo-random generator circuit that uses a pair of 4021 logic ICs fed by a simple RC clock. There are many variants using shift registers of all kinds. Here is one (scroll down a ways):
**broken link removed**

Use white noise and a comparator set at a certain level.

i think can use IC 555